[tex]\displaystyle\bf\\\frac{x^{2} -16}{3-\sqrt{x+5} } =\frac{(x^{2} -16)\cdot(3+\sqrt{x+5} )}{(3-\sqrt{x+5})\cdot(3+\sqrt{x+5} ) } =\\\\\\=\frac{(x^{2} -16)\cdot(3+\sqrt{x+5} )}{3^{2} -(\sqrt{x+5})^{2} } =\frac{(x^{2} -16)\cdot(3+\sqrt{x+5} )}{9-x-5} =\\\\\\=-\frac{(x -4)\cdot(x+4))\cdot(3+\sqrt{x+5} )}{x-4} =-(x+4)\cdot(3+\sqrt{x+5} )[/tex]